The present invention relates to dispensers for dispensing chilled beverages and, in particular, it concerns an on-demand beverage cooler which employs a negative-heat-energy accumulator containing phase-change material (PCM).
U.S. Pat. No. 5,918,468 to Cassels et al. and US Patent Application Publication No. 2002/0162339 A1 to Harrison et al. both teach beverage coolers which incorporate a quantity of phase-change material (PCM). In both cases, however, a heat pump device is thermally coupled primarily to a conduit through which the liquid flows, with the phase-change material merely providing additional thermal inertia for a more uniform cooling effect. Where a PCM with a transition temperature not much above zero Celsius is used, operation of the heat pump under zero flow conditions would be likely to lead rapidly to freezing of any water-based beverage within the conduit.